Oct. 15, 2013: New York City Republican mayoral candidate Joe Lhota, left, and Democratic mayoral candidate Bill de Blasio, participate in their first televised debate at WABC/Channel 7 studios in New York.
(AP/Pool The Daily News)

NEW YORK – Republican Joe Lhota on Wednesday released the New York City mayoral campaign's harshest ad to date, using footage of a recent biker gang attack to suggest that the city would return to its violent, crime-filled past if Democrat Bill de Blasio is elected.

Lhota, a former deputy mayor to Rudolph Giuliani who is trailing badly in the polls, centers the ad around the dramatic video of the biker attack that left several people, including a young father, injured. It then segues into harrowing black-and-white images from the 1970s and `80s, including footage of an overturned police car, a man holding a gun and corpses sprawled on the ground.

The 30-second spot, which will air on the city's broadcast networks, warns that de Blasio has a "recklessly dangerous agenda on crime" because the public advocate suggested that he would meet with biker groups.

The ad, by far the most negative in an increasingly nasty campaign, comes on the heels of Lhota's accusations during a Tuesday night debate that de Blasio is "untested" and unable to continue the city's historic reduction in crime that began in the 1990s under Giuliani. Lhota has frequently criticized de Blasio for wanting to reform the police department's stop-and-frisk policy, which allows officers to stop anyone deemed acting suspiciously.

The Democrat's campaign called the ad "divisive."

"Lhota is right that we can't go back," said de Blasio spokesman Dan Levitan. "We shouldn't return to the days when Republicans like Giuliani used fear tactics to divide New Yorkers against each other."

The ad's aggressive tone was the same tenor Lhota planned to use Tuesday night in the first of the candidates' three debates, but he was frequently put on the defensive by de Blasio.

The Democrat, up nearly 50 points in some polls, surprised observers who expected him to stick with his recent strategy, one typical of front runners, of staying above the fray and avoiding gaffes. Instead, he attacked Lhota and prevented the Republican from delivering the blows his struggling campaign desperately needed.